• Oleg Nesterov's avatar
    uprobes/x86: Fix the wrong ->si_addr when xol triggers a trap · b02ef20a
    Oleg Nesterov authored
    If the probed insn triggers a trap, ->si_addr = regs->ip is technically
    correct, but this is not what the signal handler wants; we need to pass
    the address of the probed insn, not the address of xol slot.
    
    Add the new arch-agnostic helper, uprobe_get_trap_addr(), and change
    fill_trap_info() and math_error() to use it. !CONFIG_UPROBES case in
    uprobes.h uses a macro to avoid include hell and ensure that it can be
    compiled even if an architecture doesn't define instruction_pointer().
    
    Test-case:
    
    	#include <signal.h>
    	#include <stdio.h>
    	#include <unistd.h>
    
    	extern void probe_div(void);
    
    	void sigh(int sig, siginfo_t *info, void *c)
    	{
    		int passed = (info->si_addr == probe_div);
    		printf(passed ? "PASS\n" : "FAIL\n");
    		_exit(!passed);
    	}
    
    	int main(void)
    	{
    		struct sigaction sa = {
    			.sa_sigaction	= sigh,
    			.sa_flags	= SA_SIGINFO,
    		};
    
    		sigaction(SIGFPE, &sa, NULL);
    
    		asm (
    			"xor %ecx,%ecx\n"
    			".globl probe_div; probe_div:\n"
    			"idiv %ecx\n"
    		);
    
    		return 0;
    	}
    
    it fails if probe_div() is probed.
    
    Note: show_unhandled_signals users should probably use this helper too,
    but we need to cleanup them first.
    Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
    Reviewed-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    b02ef20a
traps.c 21.2 KB